Transportation means

ABSTRACT

Means of transportation comprise a vehicle and guidance means for the vehicle. The guidance means include a plurality of stationary guide members which respectively extend parallel to alternative routes for the vehicle, which routes either branch, or join, or both. A plurality of follower members are separately mounted on the vehicle and individually engageable with the guide members, and means carried by the vehicle enable any one of the follower members to be engaged with the corresponding guide member whereby to select and cause the vehicle to follow the route corresponding to the guide member engaged.

I Unlted States Patent 1191 1111 3 777 667 Perrott Dec. 11, 1973 [5TRANSPORTATION MEANS 3,234,891 2/1966 1111111 11611 et a1. 105/2153,391,652 7/1968 Lauber 104/247 [76] Inventor- Franc Perm, h Manor2,972,966 2/1961 BOUl'dOll .1 104 247 [1011861 South Carney,clrencestefi 3,113,529 10/1963 Maestrelli... 1. 104/247 England3,254,608 6/1966 Alden 1 104/149 Filed Oct 19 1971 3,500,765 3/1970Easton et a1 104/23 [21] Appl. No.: 190,627 Primary Examiner-Gerald M.Forlenza Related U S Application Data Assistant Examiner-Robert SaiferAt -1 S Th [63] Continuation of Ser. No. 779,977, Nov. 29, 1968, tome),rvmg ompson abandoned.

[57] ABSTRACT [30] Foreign Application Priority Data Means oftransportation comprise a vehicle and guid- Aug. 21 1968 0163113116111139 883/68 means for the Vehicle- The guidance means clude a plurality ofstationary guide members which 52 U.S. c1 104/88,'104/130, 104 243respectively extend Parallel to alternative routes for 51 1111. c1 B61b13/08, B6lb 1/00 the vehicle, which either branch or Join, or [58] Field61 Search 104/88, 105, 130, both- A plurality of follower members areSeparately 104/245 246, 247 mounted on the vehicle and individuallyengageable with the guide members, and means carried by the ve- [56]References Cited hicle enable any one of the follower members to beUNITED STATES PATENTS engaged with the corresponding guide memberwhereby to select and cause the vehicle to follow the gir Agg Lfi routecorresponding to the guide member engaged. 3:098:454 7/1963 Maestrelli104/247 10 Claims, 18 Drawing Figures mmnaunec 1 1 197a 3.777.667

SHEET 1 OF 6 INVENTOR Fxm/vc/s Cm/L PER/@077 ATTORNEYS PATENTEUDEC 1 1.I915 SHEET 5 OF 6 wQW m9 m3 INVENTOR. CeAA/c/s' dye/A PER/e077 M C25 4.ATTORNEYS PATENIED-Mc 1 1 1975 SHEET 6 BF 6 FIG/g INVENTOR [Em/cm Cy/e/LPER/P077 ATTORNEYS l TRANSPORTATION MEANS This is a continuation, ofapplication Ser. No. 779,977, filed Nov. 29, 1968, now abandoned.

This invention relates to guided land transportation, and has for one ofits objects to provide means of transportation in which stationary guidemembers respectively extend parallel to alternative track routes, andare selectively engageable by follower members mounted on a vehicle inorder to select the route to be followed by the vehicle.

With common track guidance systems, such as in rail transport, vehicleposition information is supplied to a stationary position, such as asignal'box, and points, signals and the like are adjusted to meetestimated requirements.

The invention has for a further object to provide a track-guided vehiclein which the route-choice function is carried out by means carried byeach vehicle itself, and in which points, track switches and the likeare eliminated. Thus each vehicle selects its own route, preferably bymeans of a programming member carried by the vehicle.

Other objects and features of the present invention will appear morefully below from the following detailed description considered inconnection with the accompanying drawings which disclose severalembodiments of the invention. It is to be expressly understood, however,that the drawings are designed for purposes of illustration only and notas a definition of the limits of the invention, reference for the latterpurpose being had to the appended claims. In the drawings:

FIG. 1 is a somewhat diagrammatic end view ofa vehicle and associatedtrack guidance means in accordance with one embodiment,

FIG. 2 is a corresponding track plan view,

FIG. 3 is a view similar to that of FIG. I, but of another embodiment,

FIG. 4 is a similar view of a further embodiment,

FIG. 5 is a fragment of FIG. 4 illustrating one guidance,

FIG. 6 is again a similar view of yet another embodiment,

FIG. 7 is again a similar view ofa yet further embodiment,

FIG. 8 is a similar view of an embodiment utilising a linear inductionmotor for propulsion,

FIG. 9 is a lateral sectional view of another embodiment,

FIG. 10 is a fragment of the view of FIG. 9, showing an alternativeguidance condition,

FIG. 11 to 13 illustrate track forms for the embodiment of FIGS. 9 and10,

FIGS. 14 and 16 are lateral sectional views of alternative air cushionbearings for use to support a vehicle according to the invention,

FIG. 17 is a lateral sectional view of yet another embodiment, and

FIG. 18 is a plan view of the embodiment of FIG. I.

In the embodiment of FIG. 1 the vehicle 1 is supported by means such asa fluid cushion 2 on a single plane track surface 3. Alternatively, dualtrackways may be provided for support wheels (not shown), and propulsionmay be by any suitable means, such as wheels, linear induction, orairscrew. For simplicity, means of propulsion are not shown in FIG. 1.Guidance is normally by a side-rail 4, which is engaged by a followerarm member 5 mounted on the vehicle 1.

In some cases the follower arm 5 may control vehicle steering mechanismand, in such cases, a single set of follower equipment, as is beingdescribed, will suffice. In order cases, the vehicle is directly locatedin the transverse direction by the follower equipment and for thispurpose the equipment illustrated is duplicated in a transverse sectionwhich is removed from the present one. In such cases, motion of the twofollower arms 5 is synchronised, so that they both move at the sametime. In the region of each track junction as opposite side rail 6 isprovided, engageable by a pair of follower arms 7 which are normally inthe raised position shown in FIG. 1. The side guide rails 4 and 6 areeach shared by duplicated follower arms 5 or 7, this duplication beingprovided in order to prevent the vehicle 1 yawing about a vertical axis.

Referring to the track plan of FIG. 2, which is on a smaller scale thanFIG. 1, the vehicles travel from the bottom towards the top of thedrawing. A vehicle programmed to travel straight on at the junction Xcontinues guided by the lefthand guide rail 4. The track-sidetransmitter 8 transmits the vehicle a simple and ordinary signal in amanner well known, such as by a trip lever, a magnet, or a beam. Uponpassing this transmitter, a vehicle-mounted programming unit (not shown)receives this signal and is advanced one step. Such a programming unitmay comprise any of those well known in the railroad art, for example, aticket in the form of a route card, each step of which contains aspecific vehicle command either to branch left or to branch right.

If the vehicle is already programmed to branch right, it still uses thelefthand guide rail 4 for its approach and the trackside transmitter 8again advances the programming unit one step. However, in this case theprogramming unit causes the follower arm 7 to engage the guide rail 6,and subsequently the follower arm 5 is disengaged from the guide rail 4.The lower break in the FIG. 2 drawing signifies a substantial distance,so that these operations are completed before the branch junction X isreached. The vehicle is then guided to the right, by the guide rail 6,and it continues to be so guided, for the substantial distance which isrepresented by the upper break in the drawing. Subsequently, a furthertrackside transmitter 9 advances the programming unit by another step,causing the vehicle to change back to the lefthand guide rail 4. Inorder to illustrate the advantages of this system, its logicalderivation from existing road transportation will now be outlined.

The main advantage of road transportation is individual route selection.By this is meant, the ability of each individual vehcle to choose whichway it goes when the road branches. By a succession of such choices, itfollows its own selected route, to a specific destination. In order toobtain this advantage, vehicles are given complete freedom of steering,at all times. Amongst the infinite range of choice which is thusprovided, driver has continuously to select the required path. Steeringis truly of use only when the vehicle is actually choosing betweenalternative road branches and all other degrees of freedom of steeringare, from the fundamental viewpoint, not only redundant but actuallyharmful.

The feature of the present invention which has been described withparticular reference to FIGS. 1 and 2 is referred to, in principle, astrack selection Track selection retains the essential freedom of routeselection but, at other times, the vehicle is guided by the track, likea railway train. The track or tracks need be no wider than is requiredto support the vehicle wheels or other support means employed. Rigorousspeed control may be imposed, and safeguarded by automation. Thisdecreases the capital cost of track construction and, indirectly,increases its carrying capacity.

An initial application for transportation means according to theinvention could be between two points, such as an airport and a citycentre. In such a case, automatic terminal control might guide thevehicles into appropriate loop sidings, with automatic approach controlfitting the vehicles between one another, at track junctions, as theyleave the loop sidings. Speed control would prevent collisions betweenvehicles which are moving behind one another, on the same track.

At a second stage of development, a plurality of terminals could beserved by the same main line. Each vehicle would then be programmed inadvance, to select the correct sequence of lefthand and righthandbranches in the track. For example, a sequence as left," left, right,right, left, would cause the vehicle to branch left at the first branchof the track, corresponding to the first step in its programming unit orticket, left at the second branch, corresponding to the second step inthe vehicle-mounted programming unit described above, and so on. By thismeans alone, each vehicle would be directed to its prescribeddestination.

These developments, and those which are'about to be described withparticular reference to the remaining drawings, all tend to increase thetrack carrying capacity, both relative to the area occupied and the lossof urban amenity, and also in relation to the capital cost of trackconstruction. The ultimate level of carrying capacity, ofa single track,is very high, and thus it is economicto sacrifice some of this potentialcapacity in order to reduce vehicle unit size, with consequentadvantages relating to the maintenance of urban amenity and cost oftrack construction.

In order to illustrate the additional advantages which result fromfurther development, the logical derivation of this system from existingrail transportation will now be outlined. The main advantage of railtransportation is carrying capacity, both relative to the space occupiedby the track and to the cost of track construction. The maindisadvantage is that it has to use large trains, between large terminalsand/or intermediate stations, i.e., there is a lack of route choiceflexibility. The carrying capacity is obtained by vehicle guidance.However, this capacity is restricted by the need for block control,which necessitates large stretches of unused track, between each sectionwhich is actually in use, beneath the wheels of a passing train. Inorder to minimize this waste of space, long trains are used, therebyincreasing the ratio of track used to track wasted. Long trains imposethe ultimate limit on carrying capacity, by their requirement forterminal facilities, they also destroy the route choice flexibilitywhich is an important passenger requirement.

By transferring the route-selection faculty from a trackside signal boxto each individual vehicle concerned, track selection goes a long waytowards eliminating the need for block control. It is proposed tocomplete this elimination, in a system of transportation according tothe present invention, by the use of automation in conjunction withimproved vehicle braking. Not only does this enable vehicles to runcloser together, but it eases the terminal bottleneck. This is becausevehicles which are travelling close behind one another can be directedinto separate loop sidings, which are off the main track. Thus aplurality of smaller and more conveniently situated terminals becomesavailable. In terms of long-term development potential, the number ofsecondary tracks which feed a main line increases. As main line trafficdensity progressively in creases, the aim is to form groups ofindependent vehicles which maintain light end-to-end contact with oneanother. Vehicle mounted automatic speed control is provided, to causevehicles running close together to establish this end-to-end contactwithout shock. In order to avoid instability, and to minimise the numberof trains so formed, speed control preferably either always speeds up afollowing vehicle, to contact the one in front, or vice versa. Suchtrains can be longer than customary railway trains, because they escapethe limits imposed by starting and stopping facilities. At branches theyseparate out, and proceed to their separate destinations. Provided thatgaps so formed are reasonably small, they are subsequently automaticallyclosed up again.

A secondary advantage which results from forming groups in the foregoingmanner is that it eliminates the problems associated with collectivestability between vehicles running close together, but not in contact.The limit to a main line carrying capacity is no longer terminalfacilities, together with train length, but the acceptable waiting timewhile one train is waiting to enter a section of main line, behind aprevious one which is passing. While a train is waiting, other vehiclesmay arrive at the rear and establish contact with it. At the right time,they are started by computer, so as to follow the train which has justpassed. By the elimination of block control and by the use of longtrains of vehicles in light end-to-end contact, the ultimate limit ofcarrying capacity is very high indeed. The following description appliesto a design study proposing a system utilising very light individualvehicles.

The proposed system will carry in the order of 20 times as manypassengers per hour as a double threelane motorway, yet its track isonly one sixth of the corresponding width while only one half of thecorresponding clearance height above the track is required. Small andlight driverless vehicles are individually programmed in advance, sothat each follows its own independent route, even over the most complextrack network, without the need to reduce speed. Urban terminals aresituated actually inside the larger buildings, in order to reduce rushhour street congenstion, and suburban terminals are adjacent car parkschosen for road access.

Various alternative embodiments of the track selection principle willnow be described. In respect of features not individually specified,these generally resemble those already described with particularreference to FIGS. 1 and 2.

FIG. 3 of the drawings illustrates a transverse section through avehicle 10 designed for factory goods distribution, which is a possibleinitial application with low development costs. The vehicle is in theform of a truck which runs on wheels 12 over factory floor 13. It isguided either by a follower member 14 engaging a floor slot 15, asshown, or by a follower l6 engaging a floor slot 17. A programming unitselects the appropriate channel follower 14 or 16 at each branch orjunction, to route the truck to its required destination.

FIGS. 4 and 5 illustrate one application of the invention to theWestinghouse so-called transit expressway. The vehicle 18 is supportedon double pneumatic-tired wheels 19 which run on spaced track members 20and 21. Transverse guidance is provided by two horizontal wheels 22 and23 with vertical axes of rotation, which engage channel members 24 and25 beneath the top webs 26 of which the wheels 22 and 23 engage with akeying effect in order to prevent all possibility of the vehicleoverturning. In the existing system the track is without branches, orjunctions, in the normal sense and the wheels 22 and 23 engage a singlecentral channel member below the vehicle thus if it is desired to movethe vehicle 18 on to another track it is stopped on a section of trackwhich is slidable transversely and the vehicle and track section movedbodily to realign with second track. This is inconvenient for operationat high traffic densities, because the main line is out of acmembers 24and 25 above'thc track members 20 and 21 results in much increasedstability as well as providing for track selection, and supplementaryvehiclemounted horizontal guide wheels27 and 28 can be raised or loweredalong their vertical axes. The wheel 27 is shown lowered in FIG. 4, toengage a vertical track side face 29 which, in this case, is provided bya filling piece 30 in the corresponding main track member 20. A similarfilling piece 32 in the other track member 21 provides a side face 33.

At a track branch the members 24 and 25 separate, the vehicle 18 beingguided by wheels 22 and 27, with the wheel 25 temporarily disengagingthe side member 25. FIG. 5 shows the corresponding operating positionfor right-hand branches, or forjunctions from the right. The wheel 27 israised, and the wheel 28 is lowered. When the members 24 and 25separate, the wheel 22 is temporarily disengaged from the member 24 andthe vehicle 28 is guided by the wheels 23 and 2 8.

In FIG. 6 there is illustrated the application of the invention to theBrush Electrical so-called automatic self-routing taxi system. Thevehicle is supported on pneumatic-tired wheels 41 which run inside asingle channel-shaped track 42,'as compared with the spaced twin tracksof the existing proposal in which automobile-type steering is providedand controlled by an electric pick-up arm which engages an overheadguide track. On approaching a branch, this pick-up arm is given a biasto whichever side of the branch the vehicle is to follow and there isthe considerable disadvantage that the arm is affected by vehiclerolling motion, and thus the system has limited margins of robustness,sta bility and safety.

In the present application of track selection, additional horizontalwheels 43 and 44 follow surfaces of curb members 45 and 46 which areperpendicular to main track surface and in effect form side webs of thetrack member 42. These wheels 43 and 44 may be preloaded in order tomaintain contact at all times, with one or other wheel used forsteering.

44 are connected with servo-mechanism which operates to maintainpressure with whichever curb member 45 or 46 is being used for guidance.

According to yet another construction, the servomechanism is omitted,and the vehicle steers to maintain pressure with the appropriate curbmember 45 and 46, and such pressure is limited by vehicle steeringcharacteristics, e.g., castor action, or by placing horizontal wheels infront of the vehicle wheels carrying the weight, so that contact withthe curb produces a correcting couple. The curb members 45 and 46temporarily separate at branches and junctions, and the vehicle is thenguided by the lefthand curb member 45, for lefthand branches andjunctions, and by the righthand curb member 46 for righthand branchesand junction.

An embodiment of the invention with certain advantages, especially foroutdoor vehicular transportation, is illustrated in FIG. 7. The vehicle50 runs on pneumatic-tired road wheels 51 and 52 over plane surfacedtracks 53 and 54, the surfaces 55 and 56 of which lie on the sametransverse straight line and are inclined to the horizontal. The axis ofrotation of the wheels 51 and 52 is parallel to the main track surface55 and 56. FIG. 7 represents conditions for lefthand branches andjunctions and between branches and junctions. A vehicle mounted wheel'57 has an axis of rotation which is perpendicular to main tracksurfaces, and it engages a perpendicular track guide surface 58 on aside guide member 59.

A further vehicle mounted guide wheel 60 has an axis of rotationperpendicular to the main track surfaces, and it can be lowered alongits axis of rotation to engage a perpendicular guide surface 61 formedon the track member 54. This is the position for righthand branches andjunctions from the right, and the wheel 57 temporarily disengages fromthe guide track surface 58 under those conditions. It will be noted thatthere is no mean side-thrust on the wheels 51 and 52, because any suchthrust would result in transverse dift of the vehicle 50 and thusre-establish equilibrium.

At junctions and branches, each has a section of main track surfacewhich is shared by the wheels 52, of vehicles branching or joining to orfrom the left, and by wheels 51 of vehicles branching or joining to orfrom the right. Thus the track members 53 and 54 have surfaces lying inthe same transverse line.

Advantages of this system are that the inclination of the track surface55 and 56 provides a reaction force upon the vehicle 50, which locatesit transversely against side guide track surface 58. ,Thus the need fora second similar surface on the other side is eliminated. Anotheradvantage is that stones, snow and the like slide off the track, and itis less likely that pedestrians will walk upon it. It also provides theopportunity to ensure fail-safe vehicle removal to the left, at anybranch.

FIG. 8 illustrates the application of track-selection to a vehicle ofthe type known as a tracked Hovercraft," with propulsion by linearinduction. A corresponding form would suit the Bertin so-calledaerotrain. The vehicle 70 rides on air cushions 71 and 72 above atrackway 73 the upper track surface 74 of which is inclined to thehorizontal atabout degrees, for the same reasons as with the wheeledembodiment of FIG. 7. The drawing shows conditions for lefthand branchesand junctions. Transverse location is provided by a vehicle located aircushion member 75 which slides on a side guide track 76 the guidesurface 77 of which is generally perpendicular to the main track surface74. An alternative vehicle-mounted air cushion member 78 is providedwith means for lowering, to engage the perpendicular track side guidesurface 79, and it is so lowered for righthand branches and junctionswhen the cushion member 75 is temporarily disengaged from the guidetrack 76. Conductor strips 80 and 81 are provided for propulsion bylinear induction, and they are parallel to the main track surface 74 andeach suitably supported at its outer extremity. At branches andjunctions, the distance between the conductor strips 80 and 81 istemporarily increased and the vehicle is then propelled, as appropriate,by only one strip with the other strip sliding transversely from the gapbetween the magnets concerned. This avoids the need for articulatedmagnets for linear induction.

The embodiment shown in FIGS. 9 and 10 is a development of that of FIG.8 which is especially suitable for fluid cushion slipper bearingsdesigned to operate at higher pressures than are usually employed forHovercraft. It is also suitable for use where the slipper bearings,which are described by way of example, are replaced by wheels. lncreasedslipper bearing pressures reduces the track surface width requirementand economic and aesthetic considerations then demand use of a reducedtrack width. The reduced track width tends adversely to affect rollingstability, and according to this embodiment the side guide track member90 is removed from main track surface 91 by a transverse distancesufficient to provide a satisfactory lever arm for adequate rollingstability. It is provided with one or two slipway surfaces suitablyangled to ensure rolling stability, i.e., with a component of area whichis sufficient for the purpose and perpendicular to the local directionof motion in rolling.

The body of the vehicle 92 is a circular member, and the weight iscarried by the inclined resin-faced slipway surface 91 on afactory-produced and prestressed concrete beam member 93. The side trackmember 90 provides a slipway surface 94 perpendicular to main slipwaysurface 91 and engageable by a fluid cushion slipper bearing 95. It alsocomprises opposed slipway surface 96 and 97 parallel to the main slipwaysurface, and engageable by fluid cushion slipper bearings 98 and 99which provide rolling stability while the bearing 95 provides transverselocation. Duplicated equipment, similar to that just described, providesstability in respect to yawing about a vertical axis.

FIG. 9 shows the condition between junctions and branches, and forlefthand branches and junctions. The slipper bearing 95 is pre-loaded bya component of reaction from the main slipway surface 91 which isengaged by the vehicle support slipper 100 and acts to the left.Propulsion is by linear induction, utilising vehiclemountedelectromagnets 101 and 102, which are energized through track-mountedconductor strips, 103, 104 and 105. Suitable vehicle-mounted electricalpickups are provided, as shown diagrammatically at 106, and thepropulsion conductor strip 107 is parallel to main slipway surface 91.An additional fluid cushion slipper bearing 108 is provided, with meansfor rotation about an axis 109, and is shown in the raised position.

The conditions for righthand branches and junctions are shown in FIG.l0.-The fluid cushion slipper bearing 108 is lowered to engage the sideslipway surface 110, which is perpendicular to the main slipway surface91, and to the direction in which slipper bearing 108 is movable.Vehicle transverse location is then by the slipper bearing 108 opposedby a transverse component of reaction from the main slipway surface 91.A second linear induction conductor strip 111 is engaged, and this isalso parallel to the main slipway surface 91. Electromagnets for linearinduction are duplicated at 1 l2 and 113, as are the conductor stripsand associated electrical pickups. Rolling stability is still providedby the righthand side track 114, through slipper bearings 115 and 116which art upon opposed slipway surface 117 and 118, again both parallelto the main surface 91.

At junctions and branches the two side tracks and 114, together with thelinear induction equipment, are separated, in the same way as alreadydescribed for the embodiment of FIG. 8. Not only are the linearinduction strips 107 and 111 disengaged, without introducing articulatedparts, but the slipper bearings provided for stability in rolling, andfor transverse location, are similarly disengaged without articulation.The only articulated part is the subsidiary slipper bearing 108.

FIGS. 11 and 13 illustrate diagrammatically track forms suitably used.Referring particularly to FIGS. 12, which is a lateral section through alength of an overhead twin-track system, the lefthand track member isinclined to the left as in FIGS. 9 and 10 and the transverse reaction isnormally sustained by the side guide member 90. The righthand trackmember 93a is oppositely inclined, i.e. to the right, and the transversereaction is sustained by the guide member 90a on that side. The completetrack is supported on columns 119, which allow for free normal trafficbelow the track.

The invention is also concerned with the provision of suitable fluidslipper bearings for a transporation vehicle. It has been proposed thatair from a pressure vessel should penetrate a porous resistor to producea stable air film over a compliant (elastomer) faced track.Disadvantages of this proposal are that the track requires a coating ofthe elastomer, which will normally be adversely affected by sunlight andcannot be repaired without putting the track completely out of action.In addition, the porous resistor tends to become blocked, because thepore passages must be small relative to the air film thickness in orderto ensure stable film and blockage ruptures the air film, with resultanttrack damage. For these reasons, it is preferable to transfer thecompliant function to the porous resistor itself. However, in its simpleform, this is wrong in principle as the pressure differential merelyforces the resistor against track surface, sealing it.

FIG. 14 shows a solution which is provided by the present invention.Air, in an enclosed space 120, penetrates metering holes 121 which areprovided in a rigid metering plate 122. Air then passes through lowresistance holes 123 in a compliant member 124 which is of a materialsuch as a sponge rubber. Beneath the compliant member 124 there is adimpled semi-compliant facing member 125. This is of a material,preferably, which not only has the required stiffness characteristicsbut also has selflubricating and bedding properties, such as purepolytetrafluorethylene (P.T.F.E.). The

passages 123 communicate with the dimples in the facing member 125,which dimples act as ordinary aerostatic bearings to ensure a relativelythick and stable air film at 126 between the slipper bearing and arelatively smooth slipway face 127.

The compliance of the slipper bearing is sufficient to accommodate minorirregularities in the slipway surface 127 but it is at the same timesufficiently stiff to prevent air film rupture at positions between thedimples of the facing member 125. This property is important, both whencrossing irregularities in the track surface, and in the case of localzones of film instability which may be created by aerodynamicinfluences.

According to the invention, a slipper bearing such as thatjust describedmay be provided with means for pivoting, so that it can act as anordinary pivoting thrust bearing when its rubbing speed is sufficient.According to another feature of the invention, such a slipper bearing isused to provide supplementary air film lubrication beneath the primaryseal of an air slipper bearing of the type now to be described withparticular reference to FIG. 15. It may help starting and/or supplementthe hydrodynamic film locally.

FIG. illustrates a type of fluid cushion slipper bearing which could beused as a vehicle suspension unit. A soft-backed, and P.T.F.E. facedsealing ring 130 slides on a resin-faced concrete slipway member 131. Aload carrying member (for example a vehicle) 132 is supported on a fluidcushion at 133. The ring 131 provides a primary seal and leakage isprevented by secondary sealing ring 134, which slides on the primarysealing ring 130 had enough flexibility to accommodate slight ovality,so that the primary seal can pivot, advance or retreat.

A continuous fluid film is provided beneath the primary seal, andpressure in this film graduates from that inside the seal ,to thatoutside. The film provides a net upward force on the primary seal whichis hydrostatically balanced by the full interior pressure acting uponthe interior surface of the facing ring of primary seal, in conjunctionwith the exterior pressure acting on outside of seal, and springs (notshown) are provided to ensure initial sealing.

Approximate operating conditions are as follows:

Cushion pressure, 7p.s.i.

Mean net loading of primary seal on slipway, 0.02

Mean clearance 135 beneath primary seal, 0.003 inch.

It is the clearance 135 which may be stabilized by the use of thedescribed feature incorporating the semiresilient and dimpled facingmember 125. Experience with liquid bearings of this type has shown that,under favourable conditions, a hydrodynamic wedge developes between theprimary seal and the slipway surface, so that the fluid cushion becomeself-pressurising. A theoretical analysis is backed up by enough testingto show that it is possible to ensure that the net pressure of theprimary seal, upon the slipway, is of the low order stated. This reducesthe air film lubricating requirement.

FIG. 16 illusrates a developed form of fluid cushion support unit, inaccordance with the invention, which is generally circular about an axis140. At the bottom, a concrete track 141 comprises a resin-faced slipway142 upon which slides the specially balanced sealing ring assembly orprimary seal" 143. The bottom of the vehicle is at the top of thedrawing, and is represented by 144. The load is carried by a plug member145, which fits a recess in the bottom of the vehicle and is preventedfrom turning by a hollow dowel 146, which is not in the plane of thesection.

Trapped beneath the outer assembly 143 is the cushion of airwhich'supports the weight of the vehicle and provides resilience. Theair pressure is of the order of 5 to l0 p.s.i. The centre part of thiscushion at 147 is more or less disc shaped; the outer part is ahydrostatic balance chamber 148. These two spaces freelyintercommunicate. The space between the periphery of the outer plugmember and the cylindrical part of the primary seal, is closed byspecial flexible secondary seal assembly 149. When the vehicle is inmotion, the air cushion space is pressurised hydrodynamically by thesliding of the primary seal ring on the slipway. Pressure beinggenerated by the same mechanism as that for a tilting pad thrustbearing. Excess air which is generated in this way is released through abalanced nylon spool valve 150 to an exhaust belt 151 which communicateswith the atmosphere. When the vehicle is at rest the cushionis'pressurised through an induction belt 152, which is piped to acompressor discharge through the hollow dowel 146, the compressure beinginside the vehicle. At intermediate speeds a transitory regime existsconductive to lubrication failure to those sections of the sealing ringwhich are situated at specific known angles from the leading centreline. In order to prevent this, should it prove serious, hydrostaticpockets are provided, one of which is shown displaced at 153. Theprimary seal assembly is free to advance, retract or tilt in relation tothe plug member 145. Its surface loading, where it bears upon theslipway, is governed by the projected area of the hydrostatic balancechamber 144. On initial pressurisation, sealing is ensured by springs154.

The primary seal assembly 143 comprises a plastics ring member, with aninternally machined cylindrical surface and a flat ring portion 157. Thebacking cushion 158, of plastics or rubber foam, allows the tyre bearingsurface to accommodate small irregularities in the track surface 142. Aradial pressure gradient exists across the bearing surface of theprimary seal and the resultant tyre load must be matched by uniformcompression of the backing cushion, without distortion of the matingsurface from a true plane.

In the secondary seal assembly 149, a ring of pure P.T.F.E. is preloadedby a chamfered loading ring and the compression springs 154 which areretained by a cage 162. The central plug assembly comprises the securedplastic plug 145 and an outer plug member 163 seating at 164 and 165. An0 ring 166 provides a seal, and a asymmetrical bulge houses the valve150. A passage l67 restricts air flow to the interior of the plugassembly. Depression of the vehicle 144 induces air, and the equivalentspring stiffness depends on the plug interior volume with the dampinggoverned by the size of the passage 167. In an emergency the vehicle canstart without the compressor operating, and to reduce track scoring andstarting friction a plug tyre 168 of P.T.F.E. is fitted. To prevent thistyre dropping, a space behind it is vented by a radial groove 169 andvent 170.

To refer again to FIG. 6, line A A shows the axis of rotation of thewheel 43. Said wheel may be provided with a second pair of bearings,corresponding to the king-pin of an automobile, whereby the wheelbearings may pivot, about an axis B B, causing the axis of rotation ofthe wheel so to pivot. By this means, caster action may be provided, toeliminate a source of wear which would otherwise be produced by thevertical bouncing of the vehicle, due to irregularities of the maintrack surface. Similarly, such caster action may be provided for thewheel 44, and, in order to eliminate corresponding wear due toirregularities in the curb members, wheels 41 may be provided withsimilar caster action, the axes of rotation being themselves pivotableabout axes B B, in each case. Similarly, with regard to FIG. 7, one axisA A, one axis B B' and two axes C C are shown. These correspond to theaxis so named, in FIG. 6.

To refer again to FIG. 3, the wheels 12 may with advantage be placedinside members 14 and 16, as shown by 12'. By this means, the wheels donot have to cross the grooves 15 and 17.

Referring now to FIGS. 15, a hydrodynamic wedge is formed at 201 betweenthe primary seal and the slipway, by means of which the bearing isself-pressurized. Arrow 202 shows the direction of motion. An optionalduct 203 enables the bearing to be externally pressurised, by a pump orcompressor. This is of use for starting, and other circumstances whenthe self-pressurising mechanism is insufficient.

With reference to FIG. 16, the pocket 153 illustrates the application tothis embodiment of the principle shown in FIG. 14. If desired, a largepart, or the whole of tyre surface 159 may be provided with dimples; thepocket 153 corresponds to a dimple of FIG. 14. In addition, if desired,the tyre surface 153 may be a disc, not a ring. That is to say, thecentral hole may be omitted, the whole area being constructed toresemble FIG. 14. The advantage of this latter modification is that,because the semi-compliant tyre surface is in effect supported on aplurality of hydrostatic dimples, a crack in the surface of the slipwayor track, such as may normally be present at joints provided for thermalexpansion, will not rob the unit of an excessive proportion of itscarrying capacity.

The limit flange 204 is rigidly joined, in this case, by an interferencefit to the primary seal. Excessive air, or liquid, causes the outwardlyprojecting. flange of the plug member to engage this limit flange. Thiscauses the primary seal to be separated from the slipway surface,bleeding away excess air or liquid. This is an alternative or supplementto the valve 150. Its advantage is that it may limit, or accuratelylocate, the plug member, relative to the slipway, in a directionperpendicular to the slipway surface. To obtain location, without thevalve 150, an external flow restrictor may be fitted in the duct bywhich the bearing is externally pressurised.

With regard to the embodiment shown in FIGS. 15 and 16, it is emphasisedthat pressures are given only by way of example. In any particular case,pressures widely different from those described may be used. This isparticular the case should a liquid, such as oil or water, be usedinstead of air. In this case, a means is provided, such as a sprayer, tointroduce the liquid to the leading edge of the bearing, or topressurise it from an external pump. The advantage of a liquid is thatpressures of a higher order may be used, with correspondingly increasedcarrying capacity.

FIG. 17 shows an embodiment wherein a vehicle 205 is supported by wheels206 above a track 207. Magnetic elements 208 and 209 are embedded in thetrack. Follower members are provided by vehicle-mounted sensingelements, which operate in pairs, 210, 211 on the guide member 208,and/or 212, 213, on the guide member 209.

FIG. 18 is plan view of the embodiment shown in elevation in FIG. 1.Vehicle 1 rides track 3, already described in this particular case, itis provided with two pairs of follower members, 5,5 and 7,7 whichoperate on the alternative guide members 4 and 6.

I claim:

1. Means of transportation comprising a vehicle, a track having aselective branching zone and at least two alternative branching routesfor the vehicle, at least two alternative guidance means for thevehicle, each guidance means comprising at least two permanentlystationary guide surfaces extending continuously along the track,through the branching zone parallel to the same one of said branchingroutes an one of which said surfaces is inwardly facing, twovehicle-mounted primary followers individually associated andrespectively engageable with the inwardly facing guide surfaces of theguidance means, and at least one vehicle-mounted secondary followerdisposed closer to the longitudinal center line of the vehicle than saidinwardly facing guide surfaces and operable upon the other of saidsurfaces in such manner that the vehicle may be selectively constrainedtransversely of the track to cause the selected primary follower tofollow the engaged guide surface and thus lead the vehicle into theselected branching route with disengagement of the other primaryfollower from the associated guide surface being achieved solely as aresult of the transverse relative movement of the vehicle away from thatguide surface.

2. Means of transportation according to claim 1, wherein said other ofsaid guide surfaces is the surface of the track on which the vehicle issupported.

3. Means of transportation according to claim 1, wherein said other ofsaid guide surfaces of each guidance means is outwardly facing and iscloser to the center line of the vehicle than is each of the inwardlyfacing guide surfaces.

4. Means of transportation according to claim 3, wherein each guidancemeans comprises at least three permanently stationary guide surfacesengageable by at least three vehicle-mounted followers at least two ofwhich followers are individually associated with respective ones of saidguide surfaces, and by means of the en gagement of which followers withsuch guide surfaces a couple is produced which acts upon said vehicle tocounteract the rolling couple resultant from a change of direction dueto said branch in the vehicle route.

5. Means of transportation according to claim I, wherein both of saidinwardly facing guide surfaces are above the level of the track at whichthe weight of the vehicle is supported.

6. Means of transportation according to claim 5, wherein said secondaryfollower comprises a wheel on which the weight of the vehicle ispartially supported on the track, which wheel has means for steering inorder to maintain contact between the selected primary follower and theinwardly facing guide surface engaged thereby.

7. Means of transportaton according to claim 6, wherein contact betweenthe primary follower selected and the associated inwardly facing guidesurface engaged is maintained by pressure resulting from the vehiclesteering, which pressure is limited by steering castor action.

8. Means of transportation according to claim 1, wherein said two guidesurfaces of each guidance means are respective provided by twopermanently stationary guides.

9. Means of transportation according to claim 8, wherein at least one ofthe stationary guides presenting said inwardly facing guide surfaces hasan inwardly extending flange engageable by a surface associated with thecorresponding primary follower whereby the latter is restrained fromlifting in order to retain the vehicle on the track, from which flangethe follower-associated surface is disengaged at the track branch solelyas a result of the transverse relative movement of the followerconcerned away from the guide surface engaged.

10. Means of transportation according to claim 1, wherein said vehicleis propelled by linear induction means, and the linear induction meanscomprise a permanently stationaryconductor strip which branches tofollow the separate branching track routes and which has an operativesurface parallel to the surface of the track, and a vehicle-mountedlinear motor with magnet assemblies permanently stationary relative tothe vehicle, which magnet assemblies at the track branch movetransversely over the operative surface of the conductor strip so as toleave the branch of the strip following the track route not selected andto follow the strip branch following the selected route.

1. Means of transportation comprising a vehicle, a track having aselective branching zone and at least two alternative branching routesfor the vehicle, at least two alternative guidance means for thevehicle, each guidance means comprising at least two permanentlystationary guide surfaces extending continuously along the track,through the branching zone parallel to the same one of said branchingroutes an one of which said surfaces is inwardly facing, twovehicle-mounted primary followers individually associated andrespectively engageable with the inwardly facing guide surfaces of theguidance means, and at least one vehicle-mounted secondary followerdisposed closer to the longitudinal center line of the vehicle than saidinwardly facing guide surfaces and operable upon the other of saidsurfaces in such manner that the vehicle may be selectively constrainedtransversely of the track to cause the selected primary follower tofollow the engaged guide surface and thus lead the vehicle into theselected branching route with disengagement of the other primaryfollower from the associated guide surface being achieved solely as aresult of the transverse relative movement of the vehicle away from thatguide surface.
 2. Means of transportation according to claim 1, whereinsaid other of said guide surfaces is the surface of the track on whichthe vehicle is supported.
 3. Means of transportation according to claim1, wherein said other of said guide surfaces of each guidance means isoutwardly facing and is closer to the center line of the vehicle than iseach of the inwardly facing guide surfaces.
 4. Means of transportationaccording to claim 3, wherein each guidance means comprises at leastthree permanently stationary guide surfaces engageable by at least threevehicle-mounted followers at least two of which followers areindividually associated with respective ones of said guide surfaces, andby means of the engagement of which followers with such guide surfaces acouple is produced which acts upon said vehicle to counteract therolling couple resultant from a change of direction due to said branchin the vehicle route.
 5. Means of transportation according to claim 1,wherein both of said inwardly facing guide surfaces are above the levelof the track at which the weight of the vehicle is supported.
 6. Meansof transportation according to claim 5, wherein said secondary followercomprises a wheel on which the weight of the vehicle is partiallysupported on the track, which wheel has means for steering in order tomaintain contact between the selected primary follower and the inwardlyfacing guide surface engaged thereby.
 7. Means of transportatonaccording to claim 6, wherein contact between the primary followerselected and the associated inwardly facing guide surface engaged ismaintained by pressure resulting from the vehicle steering, whichpressure is limited by steering castor action.
 8. Means oftransportation according to claim 1, wherein said two guide surfaces ofeach guidance means are respective provided by two permanentlystationary guides.
 9. Means of transportation according to claim 8,wherein at least one of the stationary guides presenting said inwardlyfacing guide surfaces has an inwardly extending flange engageable by asurface associated with the corresponding primary follower whereby thelatter is restrained from lifting in order to retain the vehicle on thetrack, from which flange the follower-associated surface is disengagedat the track branch solely as a result of the transverse relativemovement of the follower concerned away from thE guide surface engaged.10. Means of transportation according to claim 1, wherein said vehicleis propelled by linear induction means, and the linear induction meanscomprise a permanently stationary conductor strip which branches tofollow the separate branching track routes and which has an operativesurface parallel to the surface of the track, and a vehicle-mountedlinear motor with magnet assemblies permanently stationary relative tothe vehicle, which magnet assemblies at the track branch movetransversely over the operative surface of the conductor strip so as toleave the branch of the strip following the track route not selected andto follow the strip branch following the selected route.